## 6 Conclusions  
In this paper, a new hydraulic engine mount design is introduced that is amplitude-sensitive, but without a decoupler. The elimination of the decoupler in this new design will eliminate issues seen in the field with hydraulic engine mounts with a decoupler. Experimental data documented in the literature have shown that the majority of hydraulic engine mounts with a decoupler do not act as vibration isolators but as hydraulic dampers. The new hydraulic engine mount design proposed in this paper still acts as a vibration isolator, yet it is amplitude-sensitive and capable of limiting engine motions brought on by \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Engine Mount Type**} & **Dyn. Stiffness** & **Dyn. Stiffness** & **\% Increase** & **Dyn. Stiffness** & **Dyn. Stiffness** & \\  & **@Notch at** & **@Notch at** & **in Stiffness** & **@Peak at** & **@Peak at** & **Dyn. Stiffness** \\  & \(\pm\)**0.1 mm** & \(\pm\)**0.4 mm** & **as Displ.** & \(\pm\)**0.1 mm NL** & \(\pm\)**0.4 mm-NL** & **@Peak (Linear)** \\  & & & & & **Spring** & \\ \hline \multirow{2}{*}{Bilinear} & \(0.071\times 10^{6}\) & \multirow{2}{*}{\(0.19\times 10^{6}\) N/m} & \multirow{2}{*}{165\%} & \multirow{2}{*}{0.90 \(\times 10^{6}\) N/m} & \multirow{2}{*}{\(1.18\times 10^{6}\) N/m} & \multirow{2}{*}{3.88 \(\times\) 10\({}^{6}\) N/m} \\  & N/m & & & & & \\ \hline \multirow{2}{*}{NL-Spring} & \(0.067\times 10^{6}\) & \(0.103\times 10^{6}\) & \multirow{2}{*}{52\%} & \multirow{2}{*}{2.56 \(\times\) 10\({}^{6}\) N/m} & \multirow{2}{*}{\(0.87\times 10^{6}\) N/m} & \multirow{2}{*}{3.88 \(\times\) 10\({}^{6}\) N/m} \\  & N/m & N/m & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Dynamic stiffness at the notch and at the peak frequencies for the bilinear and cubic cases. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Engine Mount Type**} & **Top Chamber Max.** & **Bottom Chamber Max. Pressure at \(\pm\)0.4 mm** & **Maximum Bottom** \\  & **Pressure at \(\pm\)0.4 mm** & **Max. Pressure at \(\pm\)0.4 mm** & **Piston Displacement at \(\pm\)0.4 mm** \\ \hline Bilinear & 0.288 MPa & 0.310 MPa & \(\pm\)3.58 mm \\ \hline Cubic-spring & 0.221 MPa & 0.221 MPa & \(\pm\)2.85 mm \\ \hline Linear spring & 0.776 MPa & 0.031 MPa & \(\pm\)8.7 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Top and bottom chamber max. pressures, piston max. disp. for the bilinear, cubic, and linear spring cases. shock excitations. In addition, the stiffening effect of the engine mount at the resonant peak frequency, which is often undesirable, is considerably attenuated without impacting the depth of the notch frequency. Our simulation and experimental results indicate that using a bilinear spring in our application might be easier than using a cubic spring, since engine motions are large and the possibility of the beam going through a plastic deformation is high. The cubic spring assumption, using beams, was realized at small deflections, but plastic deformation limited its use at large deflections. Bilinear springs can be easily employed using metal springs or using a custom-designed rubber mount to create the bilinear spring effect, particularly given the fact that engine mount manufacturers have access to rubber since they are designing the hydraulic engine mounts. If beams are used to create the cubic spring, attention needs to be given to the substrate rigidity, the support column rigidity and height, and the boundary conditions, since these greatly impact the cubic nonlinear stiffness properties of the beam. Plastic deformation of the beam is also of concern, and at large deformations, the beam may experience a plastic deformation if one is not careful. Another issue to also keep in mind is the static fluid pressure. To avoid vapor bubbles being created (avoid fluid cavitation) inside the chambers, hydraulic engine mount manufacturers pressurize the hydraulic engine mounts to some static pressures.