Fatigue Life Test Of Magnesium Alloy Welded Joint And Vibration Signal Analysis Of Computer Components

The paper is divided into two parts. In the first part, the paper mainly discusses the research on the fatigue performance of welded joint samples of Magnesium alloy which is widely used in aerospace, electronics, transportation areas under constant amplitude load and random load. The research produce - test curve, which enriches the test data and has an impact on the rapid development and application of magnesium alloy. In another part, the paper focuses on the analysis on the acceleration response signal of computer parts in the process of logistics from time domain and frequency domain, which offers important guidance to the real transportation packaging design. The results are as follows.The fatigue curve from AZ31 B magnesium alloy joint fatigue test under constant amplitude load:S_rms^4.30N₀=5.14x10¹¹. The fatigue test curve under random load:S_rms^2.75N₀=1.00x10⁷. By comparing these two fatigue life curves, the paper has following conclusions:（1） fatigue ultimate strength is 20 RMS（stress root mean square value is 14.1 MPa） under constant amplitude loading; fatigue ultimate strength is 2.87 RMS MPa under random loading.（2） Material constant m two test curve of varies widely.（3） Under the same stress level, the fatigue life under random loading is far lower than under constant amplitude.The paper collects acceleration response signal of circuit boards of computer under modify ASTM standard loading, and carries on the correlation analysis of it in time domain and frequency domain. In frequency domain, we carry out the fourier transform of the response acceleration signal to get the acceleration power spectrum density function and we discuss the natural frequency of computer. In time domain, we take pretreatment on response acceleration signal. After that, we take frequency domain integral to get displacement time history curve.At the same time, we analyze the acceleration response signal under modify ASTM standard and bandlimited white noise:（1） When the load signal is gauss signal, at high load level response signal the response signal distribution does not accord with guass distribution, and it is gradually close to the guass distribution with the loss of load magnitude.（2） We use skewness and kurtosis parameter to illustrate this kind of phenomenon of non-guass distribution. When the load level is high, the value of K、S is high, and the value of K、S is close to the standard with the loss of load magnitude. The value of K、S is higher under modified ASTM standard, showing that the vibration of circuit board is fierce under modified ASTM standard. So, we can get a conclusion that the value and change law of K、S may be related to the loading waveform.（3） The product will jump up with the loading level growing high. We put 2.5 KN constraint handling on the product, finding the same rule. The nonlinear of material and structure produce the non-gaussian response signal of product.