Abstract:
A turbine engine component has an airfoil portion with a tip portion and the tip portion has at least one chamfered edge on one side. If desired, the tip portion may have a first chamfered edge on a first side and a second chamfered edge on a second side opposed to the first side. A flattened tip portion may extend between the first and second chamfered edges. A tip treatment may be applied to the flattened tip portion.

Description:
BACKGROUND 
       [0001]    The present disclosure relates to a blade tip having a chamfered configuration for reducing bending stress at the tip. 
         [0002]    Many turbine engines have fans formed by a plurality of blades. In order to obtain better fan performance, an outer air seal is provided in the form of a rub strip. Occasionally, the fan blade will rub against the outer air seal rub strip. Blade tip treatments may be needed to provide an abrasive or hardened layer for rub resistance to the seal material to protect the fan blade. These treatments may cause a fatigue debit to the fan blade. 
       SUMMARY 
       [0003]    In accordance with the present disclosure, there is provided a turbine engine component which broadly comprises an airfoil portion with at least one chamfered edge on at least one side. 
         [0004]    Further in accordance with the present disclosure, there is provided a method for creating a turbine engine component, which method broadly comprises forming a turbine engine component having an airfoil portion with a pressure side and a suction side and with at least one chamfered edge on one of the pressure side and the suction side. 
         [0005]    Other details of the method for reducing stress on a fan blade tip are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a schematic diagram depicting an embodiment of a gas turbine engine; 
           [0007]      FIG. 2  is a side view of a fan blade and an abradable outer seal; 
           [0008]      FIG. 3  is a top view of a fan blade having a tip treatment or coating applied thereto; and 
           [0009]      FIG. 4  is a mid-chord sectional view of the blade of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Referring now to the drawings,  FIG. 1  is a schematic diagram depicting an exemplary embodiment of a gas turbine engine. As shown in  FIG. 1 , engine  100  incorporates a fan  102 , a compressor section  104 , a combustion section  106 , and a turbine section  108 . Various components of the engine are housed within an engine casing  110  that extends along a longitudinal axis  114 . The fan  102  is housed within a casing  116 . 
         [0011]    The fan  102  consists of a plurality of fan blades  120  which are mounted to a disk  122 . Each of the fan blades  120  has an airfoil portion  123  with a leading edge  124 , a trailing edge  126 , a root portion  128 , and a tip portion  129 . Each fan blade  120  is attached to the disk  122  at the root portion  128 . The fan blades  120  may be formed from any suitable material known in the art. For example, the fan blades  120  may be formed from an aluminum alloy. If desired, the fan blades  120  may be hollow. 
         [0012]    If desired, as shown in  FIG. 2 , the fan casing  116  may be provided with an abradable rub strip  130 . The rub strip  130  may be formed from any suitable material known in the art. In order to protect the tip portion  129  of the fan blade  120 , a tip treatment or coating  132  may be applied. The tip treatment or coating  132  provides a surface that is capable of a rub against the abradable rub strip  130  as well as providing a barrier to corrosion of the base fan blade material. The tip treatment or coating  132  can be, but is not limited to, a hard anodized coating, an anodized coating, a plasma coating, or a plated coating. The hard coating may be a coating which results from converting the base material of the fan blade  120 , typically aluminum or an aluminum alloy, to a dense aluminum oxide coating. For some hard coatings, the coating may be impregnated with Teflon. A typical anodized coating may be an aluminum oxide, which is not as dense or thick as the hardcoat. The primary function of the coating is corrosion protection; however, some wear resistance is provided. A suitable plasma coating would be a two part system that has a ceramic topcoat. Plated coatings include those that are inexpensive, readily available, easily plated, compatible with aluminum, and viable as a rub material. Such plated coatings may comprise nickel and cobalt or an alloy of these two metals. The coating may also comprise a hard abrasive material. 
         [0013]    Referring now to  FIGS. 3 and 4 , in order to reduce the peak bending stress at the tip portion  129  of the fan blade  120  at least one chamfered edge  140  or  142  is provided on the tip portion  129 . Adjacent the chamfered edge  140  or  142  is a flattened portion  144 . 
         [0014]    In a useful embodiment, the tip portion  129  is provided with two chamfered edges  140  and  142 . The chamfered edges  140  and  142  are cut so as to leave a flat portion  144  therebetween. 
         [0015]    The tip treatment or coating  132  is applied to the flat portion  144  of the modified blade tip portion  129 . Each chamfered edge  140  and  142  may be as large as possible because larger chamfers lead to more stress reduction. The size is limited however by the need to maintain a minimum amount of flat portion  144  at the tip in order to have a surface capable of an effective tip gap and/or rub, 
         [0016]    As can be seen from  FIG. 3 , the chamfered edge  140  may be located along the suction side  144  of the fan blade  120  and the chamfered edge  142  may be located along the pressure side  146  of the fan blade  120 . Each of the chamfered edges  140  and  142  begins at a point  148  and  150  respectively spaced from the leading edge  124  of the fan blade. Each chamfered edge  140  and  142  extends to a point  152  and  154  respectively spaced from the trailing edge  126  of the fan blade  120 . At the points  148 ,  150 ,  152  and  154 , the chamfered edges  140  and  142  are blended into the pressure and suction sides  144  and  146 . The distance from the leading edge  124  of the fan blade or the trailing edge  126  of the fan blade to the chamfered edges  140  and  142  is determined based on modeshape and the stress distribution associated with it of any vibratory mode of concern where bending is present at the tip. Each of the chamfers  140  and  142  may exist at and around the peak stress chordwise location or locations so that the stress reduction is achieved. 
         [0017]    In order to ensure a smooth flow of air over the pressure and suction sides  146  and  144  respectively, a sheath  160  may be placed over the leading edge  124  of the fan blade  120 . The sheath  160  may be formed from a metal selected from the group consisting of titanium, nickel, steel, alloys of the foregoing, and any material more erosion-resistant than the material forming the fan blade  120 . 
         [0018]    Each chamfered edge  140  or  142  may be cut to have a radius or may be cut straight to create a setback of the corner and reduce the peak bending stress at the tip portion  129  where the tip treatment or coating  132  may be applied. The radius of each chamfered edge  140  and  142  or the straight cut of each chamfered edge  140  and  142  should be such as to create the flat tip portion  129 . The provision of the chamfered edges  140  and  142  reduces the peak bending stress by moving the stress points away from the tip edge. This effectively restores the fatigue strength back to the original substrate. The radius, when sued, also provides a surface that will enable treatments such as a hardcoat which has a propensity for cracking if a break edge is not provided. The value of the radius and the size of the flat tip portion  129  may be determined by which treatment is selected and overall blade requirements. 
         [0019]    The fan blade  120  of the present disclosure may be manufactured using any desired technique. For example, the fan blade  120  with the chamfered edges  140  and  142  may be manufactured using an investment casting technique in which the chamfered edge  140  and/or  142  are integrally formed with the remainder of the fan blade  120 . Alternatively, the fan blade  120  without the chamfered edges  140  and/or  142  may be manufactured using any suitable casting technique known in the art. After the fan blade  120  is cast, the chamfered edges  140  and/or  142  may be formed using any suitable cutting technique known in the art to form the edges  140  and/or  142  with a straight cut or a radius and to form the flattened tip portion  129 . 
         [0020]    After the tip portion  129  is formed, the tip treatment or coating  132  may be applied using any suitable technique known in the art. 
         [0021]    While the present disclosure has focused on fan blades, it should be recognized that the chamfered edges described herein may be applied to other types of blades and to vanes. 
         [0022]    There has been described in accordance with the instant disclosure a method for reducing stress on a blade tip. While the method set forth herein has been described in the context of a particular embodiment, other unforeseeable alternatives, modifications, and variations may become apparent to those skilled in the art. Accordingly, it is intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims.