Abstract:
An environmental chamber includes an enclosure having opposed walls each wall having an aperture of size to receive a test specimen support therethrough. The apertures are aligned with each other along on a reference axis. A forced air source is configured to supply forced air in a direction to intersect with the reference axis within the enclosure. A diverter is positioned between the forced air source and the reference axis. The diverter is configured to receive the forced air and control the air flow past different portions of the reference axis. The environmental chamber is used with a load frame having test specimen supports extending into the opposed apertures. A method of directing more force air at the test specimen supports than at at least a portion of the test specimen to maintain a selected temperature gradient in the test specimen is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 62/008,796, filed Jun. 6, 2014, having the same title, and is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. 
         [0003]    Common tests performed on polymer and metallic materials involve a cyclic or monotonic applied stress. These tests often apply tensile forces and/or compressive forces to a specimen. Specimens may include, by way of example only and not by way of limitation, tensile and compressive specimens in dog bone and cylindrical shapes, etc. Gripping mechanisms for holding specimens may include, by way of example only and not by way of limitation, tensile grips, compression platens, wedge action grips, shear grips such as double lap shear grips, tearing energy grips, bend fixtures, etc. Tests are often performed in a load frame with an environmental chamber used to expose the specimen under test to a particular thermal environment. The temperature is often controlled and usually varied throughout the test. The mechanical properties of the material are evaluated by imposing an excitation motion (or force) on the specimen and measuring the resultant force (or motion) response of the specimen. 
         [0004]    From the relationship of the response output to the excitation input, characteristics of the specimen material can be deduced. Most theoretical models for the polymers predict a response which is dependent on frequency, temperature, and amplitude. Most empirical testing maps the response as a function of varied frequency, temperature, and amplitude. One such example is the measure of the dynamic moduli of polymer materials, for instance, the storage modulus and loss modulus for dynamic mechanical analysis (DMA). In the particular case of polymer testing, since the mechanical properties (dynamic moduli) are very temperature dependent, it is important that the specimen under test be of a homogenous and stable temperature during the mechanical measurement. This thermal environment is key in obtaining repeatable and consistent empirical data. 
       SUMMARY 
       [0005]    This Summary and the Abstract herein are provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary and the Abstract are not intended to identify key features or essential features of the claimed subject matter, nor are they intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the Background. 
         [0006]    An aspect of the disclosure includes an environmental chamber having an enclosure with opposed walls each wall having an aperture of size to receive a test specimen support therethrough. The apertures are aligned with each other along on a reference axis. A forced air source is configured to supply forced air in a direction to intersect with the reference axis within the enclosure. A diverter is positioned between the forced air source and the reference axis. The diverter is configured to receive the forced air and control the air flow past different portions of the reference axis. The environmental chamber is used with a load frame having test specimen supports extending into the opposed apertures. 
         [0007]    Another aspect of the disclosure is a load frame having a support structure, an actuator connected to the support structure and a pair of test specimen supports connected to the support structure and the actuator and configured to hold a test specimen therebetween and on a reference axis, each test specimen support including a test specimen support configured to hold a portion of the test specimen. The load frame includes the environmental chamber as described above where each aperture is of size to receive one of the test specimen supports therethrough. 
         [0008]    The environmental chamber, load frame and method above can include one or more of the following features. 
         [0009]    The diverter can be configured to reduce air flow at an inner portion of the reference axis remote from each of the apertures and increase air flow at remote portions of the reference axis, each remote portion being located between the inner portion and one of the apertures. The diverter can include surfaces to deflect air flow toward each of the remote portions of the reference axis, where each of the surfaces can be oriented oblique to the air flow. 
         [0010]    The diverter can include a first of one or more apertures therethrough to direct air flow to each of the remote portions of the reference axis, and if desired, a second of one or more apertures therethrough configured to direct air flow to the inner portion of the reference axis. In one embodiment, the second of one or more apertures is disposed between a pair of said first of one or more apertures. Each of the first of one or more apertures and/or the second of one or more apertures can be disposed one or more flat members, where the flat member(s) are oriented oblique to the reference axis or parallel to the reference axis. 
         [0011]    In further embodiment, the diverter includes a mount configured to adjustably fix the diverter at a selected distance from the reference axis. The diverter can be mounted in the enclosure in a spaced apart relation to a third aperture or inlet (i.e. outlet for the forced air support) that provides forced air into the enclosure. In yet a different embodiment, the diverter is mounted so as to cover at least a part of the third aperture, where the third aperture can be disposed on a conduit adjustable in length and configured to convey the forced air. 
         [0012]    Yet another aspect is a method of maintaining a selected temperature gradient of a test specimen during application of loads or displacements with a load frame having a support structure and an actuator, comprising: supporting the test specimen in an environmental chamber with a pair of test specimen supports operably connected to the actuator and the support structure so as to hold the test specimen on a reference axis, each test specimen support having a portion extending into the environmental chamber through a corresponding aperture; and supplying forced air into the chamber; and directing more air at each of the portions of the test specimen supports than at at least a portion of the test specimen to control a temperature gradient across the test specimen during testing. 
         [0013]    In one embodiment, directing more air at each of the portions of the test specimen supports than at at least a portion of the test specimen comprises using a diverter to control air flow. The method can also include adjusting a position of the diverter in the environmental chamber and/or including one or more of the features described above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a block diagram of a load frame with heated air flow; 
           [0015]      FIG. 2  is a block diagram of a load frame with cooled air flow; 
           [0016]      FIG. 3  is a perspective view of a diverter according to an embodiment of the present disclosure; 
           [0017]      FIG. 4  is a perspective view of a diverter according to another embodiment of the present disclosure; 
           [0018]      FIG. 5  is a block diagram of a diverter enabled embodiment of the present disclosure; 
           [0019]      FIG. 6  is a block diagram of another diverter enabled embodiment of the present disclosure; 
           [0020]      FIG. 7  is an elevation view of a diverter according to an embodiment of the present disclosure; 
           [0021]      FIG. 8  is a block diagram of a diverter enabled embodiment of the present disclosure; 
           [0022]      FIG. 9  is a graph of simulated maximum and minimum specimen temperatures according to an embodiment of the present disclosure; 
           [0023]      FIG. 10  is a perspective view of a load frame with an environmental chamber; 
           [0024]      FIG. 11  is a perspective view of a portion of an environmental chamber according to one embodiment of the present disclosure; 
           [0025]      FIG. 12  is an elevation view of  FIG. 11  taken along lines  12 - 12  thereof; and 
           [0026]      FIG. 13  is an elevation view of  FIG. 11  taken along lines  13 - 13  thereof. 
           [0027]      FIG. 14  is a perspective view of an environmental chamber. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    A load frame indicated schematically at  100  in  FIG. 1  is shown in greater detail in  FIG. 10 . Load frame  100  is generally used for loading a test specimen shown schematically at  102 . The specimen  102  is located in the interior of an environmental chamber  104  forming an enclosure with a pair of end walls  106  having openings  108  through which extension support assemblies  110  extend. The chamber  104  is supported relative to the load frame  100  in any desired manner, the details of which are not pertinent to the present disclosure. Extension assemblies  110  support the specimen  102  in a load path between an excitation motion input  112  and a force transducer  114 , and each includes a test specimen support  111  typically connected to a gripping mechanism  113 , shown schematically, such as those described above. Such excitation motion inputs, force transducers, and the relative positions thereof in the test system  100  may vary depending on the specific test system employed. Nevertheless, these aspects are well known, and the details of which are not pertinent to the present disclosure. 
         [0029]    Referring to  FIG. 10 , a load frame indicated generally at  100  is shown schematically and is used for loading a test specimen shown schematically at  1011 . The specimen  1011  is located in the interior of an environmental chamber  1012  forming an enclosure with a pair of opposed end walls  1013 . The chamber  1012  can be disposed within another enclosure  1017 . The chamber  1012  is supported relative to the load frame  100  in any desired manner, the details of which are not pertinent to the present invention disclosure. As illustrated, the load frame  100  has a support structure having base  1014 , a pair of upright columns  1015  and a cross head  1016 . The cross head  1016  supports a test specimen support  1020  having aspects of the present disclosure. A similar, if not identical, test specimen support  1021  is illustrated at a lower end of the environmental chamber  1012 . In the embodiment illustrated, the test specimen support  1021  is coupled to an actuator (indicated schematically at  1019 ) that is located in the base  1014 . Such actuators are well known, the details of which are not pertinent to the present disclosure. Generally, the actuator  1019  and the support structure are configured so as to apply loads or displacements to the test specimen  1011  using the test specimen supports  1020 ,  1021 . A load cell  1018  is often provided to measure applied loads. 
         [0030]    At this point, it should be noted aspects of the present disclosure are not limited to the load frame  100  of the exemplary embodiment, nor are aspects of the present disclosure limited to only applying loads to the test specimen  1011 , although aspects of the present disclosure are particularly advantageous when loads are applied since such loads are applied through the test specimen supports  1020  and  1021 . 
         [0031]    Environmental chambers are commonly used to subject the test specimen  1011  to high or low temperature environments in order to obtain measurements indicative of properties of the test specimen  1011 . Since at least portions of the test specimen supports  1020  and  1021  are also subjected to the same or similar environment as the test specimen, the test specimen supports  1020  and  1021  (e.g., extension assemblies such as assemblies  110  schematically illustrated) must perform satisfactorily when subjected to the high or low temperature environment. In the case of load frames such as load frame  100 , the test specimen supports  1020 ,  1021  transmit or impart loads to the test specimen  1011 , and therefore, they must impart these loads when the holders  1020 ,  1021  are also operating in the high or low temperature environment. 
         [0032]    Extension assemblies  110  or supports  111  are part of test specimen grips well known in the material testing field. The mechanisms used to hold the ends of the test specimen may take any number of well-known forms including but not limited to displaceable wedges and clamping collets. Other forms of test specimen supports are illustrated in U.S. Pat. Nos. 5,095,757 and 5,945,607 and which is hereby incorporated by reference in its entirety. These and other forms of test specimen receivers can be used with aspects of the present invention herein described and/or illustrated. 
         [0033]    Environmental chambers are commonly used to subject the test specimen  102  to high or low temperature environments in order to obtain measurements indicative of properties of the test specimen  102 . As at least portions of the extension assemblies  110  are also subjected to the same or similar environment as the test specimen  102 , the thermal properties of the extension assemblies  110  are also a factor in obtaining measurements. 
         [0034]    In order to change the temperature of a specimen such as specimen  102 , thermal chambers such as chamber  104  typically used forced air flow of heated or cooled air within the chamber  104  directed across the specimen  102  and the specimen attachment region. Since the temperature range for a typical polymer test is in the −150 to 350° C. range (but not limited to this range), and as many different temperatures may be used during a test, fast temperature changes may be desired. Forced air convection is typically used over natural air convection, and a forced convection environmental chamber is the most applicable heating/cooling device to control specimen temperature quickly. 
         [0035]    The extension assemblies  110  are part of the load path defining a reference axis  107 , including at least a portion of the extension assemblies  110 , e.g. test specimen support  111 , being inside the environmental chamber  104 , and as such, high stiffness and low mass for the extension assemblies  110  is desired. A high stiffness, low mass design constraint often leads to material and geometry selections for extension assemblies  110  which have a high thermal conductive rate, and relatively lower thermal convective rate, particularly with respect to the specimen  102  under test. The extension assemblies  110  become a conductive heat transfer path from the interior of the environmental chamber  104  to components outside the environmental chamber  104 , which is most often at some temperature unequal to the desired specimen temperature and the environmental chamber air temperature. In contrast, the specimens are often polymer materials having a high thermal convective rate, and a relatively lower thermal conductive rate relative to the extension assemblies  110 . Further, the specimen diameter is also usually smaller than the diameter of the extension assemblies  110 , which results in a higher convective heat transfer for the specimen section. 
         [0036]    Extension assemblies  110  that extend into an environmental chamber are subjected to the same environmental conditions as the specimen  102  to be tested. Traditional methods by which the temperature of extension assemblies are controlled include fluid cooling or fluid heating, such as by running cooled or heated water or air through the extension assemblies. Heat draw from/to fluid cooling/heating can lead to very large temperature gradients. Further, fluid cooling or heating extension assemblies inside of an environmental chamber can be very difficult to implement. In an advantageous embodiment, extension assemblies  110  described herein are not cooled or heated, except by convective air flow in the chamber, and internal conductive heat flow. In other words, the extension assemblies  110  or supports  111  extending into the environmental chamber do not include any supplemental heating or cooling systems or features, thereby providing significant cost savings because a much simpler support can be used. 
         [0037]    In the case of a high temperature environment in the environmental chamber  104 , the air temperature is always higher than the specimen temperature. Therefore, all convective heat transfer from the air flow is into the specimen  102  and into the extension assemblies  110  as shown in  FIG. 1 , with arrows of longer length indicating a higher heat transfer rate. Specifically, horizontal arrows indicate convective transfer, and vertical arrows represent conductive heat transfer. Forced hot air indicated by arrows  116  results in convective heat transfer into the specimen  102  as indicated by arrows  118 , and convective heat transfer into the extension assemblies  110  as indicated by arrows  120 . Conductive heat transfer in specimen  102  is indicated by arrows  122 , and conductive heat transfer in extension assemblies  110  is indicated by arrows  124 . All conductive heat transfer leads out of the chamber  104  through the extension assemblies  110 . The thermal flow for this embodiment is from the forced hot air, to the specimen  102  and extension assemblies  110 , and out of the specimen  102  to the extension assemblies, and then out of the chamber  104 . 
         [0038]    In the case of a cold temperature environment in the environmental chamber  104 , the air temperature is always lower than the specimen temperature. Therefore, all convective heat transfer from the air flow is out of the specimen and out of the extension assemblies as shown in  FIG. 2 , with arrows of longer length indicating a higher heat transfer rate. Specifically, horizontal arrows indicate convective transfer, and vertical arrows represent conductive heat transfer. Forced cold air indicated by arrows  116  results in convective heat transfer from the specimen  102  as indicated by arrows  218 , and convective heat transfer from the extension assemblies as indicated by arrows  220 . Conductive heat transfer in specimen  102  is indicated by arrows  222 , and conductive heat transfer in extension assemblies  110  is indicated by arrows  224 . All conductive heat transfer leads into the chamber  104  through the extension assemblies  110 . The thermal flow for this embodiment is from the exterior of the chamber  104 , into the extension assemblies  110 , into the specimen  102  from the extension assemblies  110 , and out of the specimen  102  and extension assemblies  110  to the chamber  104 . 
         [0039]    Because of the typically different thermal qualities of the extension assemblies  110  and the specimen  102 , and the conductive heat transfer into or out of the specimen  102  from the contact with the extension assemblies  110 , there can be difficulty in obtaining a uniform temperature gradient within a specimen in the presence of a convective airflow field. Due to the relatively low thermal conductivity combined with the high convective heat transfer in the specimen  102 , the center section of the specimen  102  can form a hot spot in a heated environment ( FIG. 1 ). The high thermal conductivity of the extension assemblies  110  keep the assemblies  110  relatively cool (at least with respect to the specimen  102 ) in a heated environment, and create a heat sink for thermal energy flowing from the specimen  102  into the assemblies  110 . The relatively low convective heat transfer coefficient of the typically metallic assemblies  110  can make the thermal gradient problem in the specimen  102  even worse since the lack of convective heating from the air to the extension assemblies  110  also keeps the assemblies  110  cooler with respect to the specimen  102 . Similar difficulty is found in obtaining uniform temperature gradient within a specimen in the presence of a cooled environment ( FIG. 2 ). 
         [0040]    In one embodiment, a diverter is positioned in the forced air flow path, to divert at least some of the heated or cooled air from the center region (coinciding with an inner portion of the reference axis  107 ) of the specimen  102  to the extension assemblies  110  (each located at a remote portion of the reference axis  107  remote from the inner portion of the reference axis  107 ). The various embodiments of the diverter reduce the convective heat transfer coefficient in the specimen region, which, for example, reduces the hot spot in the center of the specimen  102 . This reduced hot spot allows a less drastic temperature gradient across the specimen vertical section. 
         [0041]    Example embodiments of diverters  300  and  400  are shown, respectively, in  FIGS. 3 and 4 . Diverter  300  is seen in perspective in  FIG. 3 . Diverter  300  has a wedge shape having wedge walls or surfaces  302  extending from a wedge apex  304  in a diverging manner. Diverter  300  may have legs  306  extending substantially parallel to one another from ends  308  of wedge walls  302  remote from apex  304 . Legs  306  in one embodiment have a semi-circular cutout  310  to reduce or prevent air flow toward a specimen. The shape of the cutout  310  can be similar to the shape of the outer surfaces of the specimen  102 , if desired. The diverter  300  is shown positioned in an air flow path in  FIG. 5  where the surfaces  302  are oriented oblique to the air flow or the reference axis  107 . 
         [0042]    Referring also to  FIG. 5 , diverter  300  placed in the flow path of air flow  116  reduces the heat transfer in the specimen region, particularly the center thereof, by reducing the amount of local air flow at the specimen  102 . Since the convective heat transfer coefficient is proportional to the quantity of air flow, lower quantity of air flow results in a lower heat transfer coefficient. The forced air flow  116  is diverted at  502  away from the center of the specimen  102 , and toward the extension assemblies  110 . This substantially reduces the amount of convective heating of the specimen  102 , and increases the amount of convective heating of the extension assemblies  110 , especially in the area  504  of the extension assemblies  110  that are closest to the specimen  102 . This additional airflow compensates for the relatively higher thermal conductivity of the assemblies  110  relative to the specimen  102  so as to increase the temperature of the extension assemblies  110 , when compared with the testing environment without the diverter  300 , and makes and/or maintains the extension assemblies  110  closer in temperature to that of the specimen  102 , reducing conductive heat flow from the specimen  102  to the extension assemblies  110  by reducing the temperature gradient between the specimen  102  and the extension assemblies  110 , and then as a result, reducing the temperature gradient within the specimen. 
         [0043]    Diverter  400  is seen in perspective in  FIG. 4 . Diverter  400  has a wedge shape similar to that of diverter  300 , having diverging wedge walls  402  extending from a wedge apex  404 . Diverter  400  has in one embodiment a plurality of openings in each of its walls  402 . The openings are smallest at  406  closest to the wedge apex  404 , and increase (e.g. gradually) to larger openings  408 ,  410 , and  412  the farther the openings are from the wedge apex  404 . While four rows of openings are shown, it should be understood that a greater or fewer number of rows of openings (or other patterns of the openings) may be used without departing from the scope of the disclosure. Further, the openings in another embodiment may have multiple rows of openings of the same size without departing from the scope of the disclosure. The diverter  400  is shown positioned in an air flow path in  FIG. 6 . 
         [0044]    Referring also to  FIG. 6 , diverter  400  placed in the flow path of air flow  116  reduces the heat transfer in the specimen region by reducing the local air flow velocity at the specimen  102  in a manner similar to that described above with respect to diverter  300 . Since the convective heat transfer coefficient is proportional to the air velocity, lower air velocity results in a lower heat transfer coefficient. The forced air flow  116  is diverted at  502  away from the center of the specimen  102 , and toward the extension assemblies  110 . Further down the legs  402  from the wedge apex  404 , the openings  406 ,  408 ,  410 , and  412  allow an increasing amount of air flow from forced air flow  116  through to the specimen  102 , as indicated at  602 , with convective heating greater near ends of the specimen  102  closest to the extension assemblies  110 , indicated at  606 . This additional airflow compensates for the relatively higher thermal conductivity of the assemblies  110  relative to the specimen  102  so as to reduce the amount of convective heating of the specimen at the center  604  of specimen  102 , and increases the amount of convective heating of the extension assemblies  110 , especially in the area  608  of the extension assemblies  110  that are closest to the specimen  102  when compared with the testing environment without the diverter  400 . This partial diversion of air flow increases the temperature of the extension assemblies, and makes and/or maintains the extension assemblies  110  closer in temperature to that of the specimen  102 , reducing conductive heat flow from the specimen  102  to the extension assemblies  110  by reducing the temperature gradient between the specimen  102  and the extension assemblies  110 , and then as a result, reducing the temperature gradient within the specimen. 
         [0045]    Diverters such as diverters  300  and  400  are in one embodiment positioned in close proximity to the specimen  102 , so as to divert as much of air flow  116  away from the specimen as desired, with at least a majority of air flow  116  directed at the specimen  102  being diverted away from specimen  102  by diverter  300 , and less air flow  116  diverted away from specimen  102  by diverter  400  in comparison to the air flow diverted by diverter  300 , with each diverter  300  and  400  reducing the temperature gradient between specimen  102  and extension assemblies  110 , and then as a result, reducing the temperature gradient within the specimen. Diverters  300  and  400  may be mounted within chamber  104  in a number of ways without departing from the scope of the disclosure. For example only and not by way of limitation, diverters could be mounted for example with support plates and/or support assemblies to an inside portion of the environmental chamber  106 , such as to a wall or a door thereof, or diverters  300  and  400  could be mounted to one or both of the extension assemblies  110  disposed in the environmental chamber  106 , or the like. 
         [0046]    Diverters such as diverters  300  and  400  are positioned as shown in close proximity to the specimen  102 . It should be understood that the exact positioning of the diverters  300  and  400  may be closer to or farther from the specimen  102  without departing from the scope of the disclosure. Further, multiple diverter designs are possible that divert air flow from the specimen  102 , or that divert more air flow toward portions of the extension assemblies  110  as opposed to the specimen  102 , and are within the scope of the disclosure. 
         [0047]      FIG. 7  shows a diverter  700  that may be used in another embodiment to reduce the temperature gradient within a specimen  102  assemblies. A smaller temperature gradient between a specimen such as specimen  102  and extension assemblies such as assemblies  110  may help to reduce the temperature gradient within the specimen. Diverter  700  in the exemplary embodiment may be considered a baffle since the diverter  700  covers or is otherwise disposed in a channel or passageway or at an end thereof through which air flow  116  is introduced onto the specimen. In this embodiment, the air flow conduit opening is circular, and the diverter  700  is therefore circular. It should be understood that different air flow conduit opening shapes may be accommodated with diverters of a shape matching the conduit opening without departing from the scope of the disclosure. 
         [0048]    Diverter  700  has a plurality of openings of different sizes therein. At a center of the diverter, openings  702  are small. At top and bottom portions  704  and  706  of the diverter  700 , openings  708  and  710  are larger than openings  702 . At sides  712  and  714  of the diverter  700 , openings  716  and  718  are larger than openings  702 ,  708 , and  710 . As air flow passes through the diverter  700 , more air moves through openings  716  and  718  than through openings  708  and  710 , and more air moves through openings  708  and  710  than through openings  702 . In one embodiment, the width  720  and height  722  of the section of the diverter  700  containing openings  702  is approximately sized to a height and width of the specimen  102 , although that need not be the case. 
         [0049]      FIG. 8  schematically shows an embodiment of an environmental chamber  104  employing a diverter  700 . Channel or passageway  800  provides forced air flow  116  into environmental chamber  104 . In this embodiment, diverter  700  covers the exit opening  801 . The relative size of the passageway  800  to the environmental chamber  106  can vary as needed. Air flow  116  is modified by the openings in the diverter  700 . Arrows  802  indicate air flow through diverter  700  openings  702 . This air flow  802  is substantially directed at specimen  102 . Arrows  808  and  810  indicated air flow through diverter  700  openings  708  and  710 . Arrows  816 ,  818  indicate air flow through diverter  700  openings  716  and  718 . The air flow represented by arrows  816 ,  818  is directed past specimen  102 , but not directly at specimen  102 , and thereby substantially bypasses specimen  102 . The lower velocity and volume of air flow indicated impinging upon the specimen  10  and represented by arrows  802  results in lower convective heating of the specimen  102  as indicated at arrows  820 , and relatively higher convective heating of extension assemblies  110  as indicated by arrows  822 . Conductive heat flow in the specimen  102  is indicated by arrows  824  and conductive heat flow in the extension assemblies  110  is indicated by arrows  826 . The air flow pattern in environmental chamber  104  as modified by diverter  700  increases the temperature of the portions of the extension assemblies  110  proximate their engagement with the specimen  102 , and makes and/or maintains the portions of the extension assemblies  110  proximate the specimen  102  closer in temperature to that of the specimen  102 , reducing conductive heat flow  824  from the specimen  102  to the extension assemblies  110  by reducing the temperature gradient between the specimen  102  and the extension assemblies  110 , and then as a result, reducing the temperature gradient within the specimen. 
         [0050]    Diverter  700  is connected to opening  801  in one embodiment by a hinge  828 , so that diverter  700  may be removed from the air flow path  116 . Alternative mountings of diverter  700  to opening  801  include by way of example only and not by way of limitation press fitting, screwing, riveting, or the like, and other mounting structures may be employed without departing from the scope of the disclosure. The mounting structures may be configured to allow easy removal of the diverter  700  such as slots or guides  830  formed in the environmental chamber  106  that engage one or more portions of the perimeter edges of the diverter  700 . Structures that allow easy removal allow diverters having different air diverting characteristics to be tried until a diverter that achieves the desired or at least acceptable temperature gradient within the specimen  102 , at least in part by reducing the temperature gradient between the specimen and the portions of the assemblies  110  proximate the specimen  102 . 
         [0051]    Cold temperature applications are the most applicable for DMA testing. The cold temperature case is similar to the hot temperature case described herein, except that air temperature is always colder than the specimen and extension assemblies, and the heat transfer path is reversed, as shown in  FIG. 2 . For cold testing, the direction of thermal energy is from the outside of the chamber  106 , through the extension assemblies  110 , into the specimen  102 , and then out of the specimen  102  and into the air flow. All benefits of the air flow diverters described herein are the same in the cold temperature case as in the hot temperature case, except that convective and conductive flow paths are reversed. 
         [0052]      FIG. 9  shows simulated maximum and minimum specimen temperatures for a 2° C. air flow temperature step (from −125 to −123° C.). The maximum temperature curve with a diverter such as diverter  700  is indicated at  902 , and the minimum temperature curve with a diverter such as diverter  700  is indicated at  904 . Maximum and minimum temperature curves without a diverter are indicated at  906  and  908  respectively. The steady state temperature gradient is much smaller with the diverter. The gradient with the diverter is small during the transient as well. 
         [0053]      FIG. 11  is a perspective view of a portion  1100  of an environmental chamber  1101 , an embodiment of a complete assembly of which is illustrated in  FIG. 14 . The environmental chamber  1101  can be mounted to load frame  100  illustrated in  FIG. 10 , or adjacent to load frame  100  on a suitable support such that portion  1100  corresponds to environmental chamber  1012  illustrated in  FIG. 10 , in which case for purposes of the present invention the environmental chamber  1101  is considered part of the load frame  100 . 
         [0054]    In  FIG. 11 , conduit  800  is shown with a diverter such as diverter  700  positioned over opening  801 . Diverter  700  is connected to conduit  800  at standoff  1102 , such as with a screw or other suitable fastening device. Conduit  800  surrounds an end of extension tube  1108  which is in air flow communication with the source of heated/cooled air flow  116 . Conduit  800  is in one embodiment connected to extension tube  1108  by a screw or other suitable fastening device extending through slot  1104 . In the embodiment illustrated, air passageway  1110  includes conduit  800  and extension tube  1108 . In one embodiment, the air passageway  1110  for air directed at the specimen is adjustable in length, which can be helpful in adjusting a position of the diverter  700  relative to a test specimen, not shown. Standoff  1102  also has a slot,  1106 , allowing for a movable mounting of conduit  800  such as in a telescoping nature with respect to extension tube  1108 . Air return from the interior of chamber  104  is in one embodiment in a space around the conduit  800 , through a suitable air return, etc. 
         [0055]      FIG. 12  is an elevation view of  FIG. 11  taken along lines  12 - 12  thereof. In this figure, the diverter  700  is not shown. Air flow  116  is directed into environmental chamber  104  through extension tube  1108  and conduit  800 , through opening  801 , which in some embodiments may be covered with a diverter such as diverter  700 . Air flow, such as air flow  116  described herein, is in one embodiment generated by fan  1202  driven by motor  1204 . Heater elements  1206  warm air to be blown by fan  1202  in one embodiment. Cooled air may be introduced in place of heated air, the provision of cooled air known to one of skill in the art, and therefore not described in detail herein. 
         [0056]      FIG. 13  is an elevation view of  FIG. 11  taken along lines  13 - 13  thereof. In this figure, the diverter  700  is not shown. Conduit  800  is shown mounted to standoff  1102 , which also serves in one embodiment as a mount for a diverter such as diverter  700  (not shown). 
         [0057]    While the systems described herein are amenable for use with specimens of all types, they are specifically amenable and cost effective for use with specimens that are elastomers or plastics. 
         [0058]    Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above as has been held by the courts. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.