| 摘要: | 本論文主要探討工程塑膠材料：丙烯腈 - 丁二烯 - 苯乙烯(Acrylonitrile-Butadiene-Styrene)(ABS)應用於製造液晶螢幕電視機後殼。使用之加工方法如下：射出成型(Injection molding)、真空熱成型(Vacuum thermoforming)等。傳統工業上，生產液晶螢幕電視機後殼是使用射出成型，然而開發射出成型於大型尺寸模具費用昂貴，所以採用另一種塑膠成型法－真空熱成型(Vacuum thermal forming)，其用於製造大型尺寸產量少之產品，模具費用相對較低，在真空熱成型過程中，將ABS塑膠材料板片進行加溫軟化後，施予真空與施加壓力，而加溫過後的ABS塑膠材料於模具孔洞成型時會產生流變行為，此時的應力、溫度、應變與應變速率會間接影響ABS塑膠材料的變型趨勢。
利用標準微型電腦材料試驗機(MTS)，對塑膠材料ABS進行高溫流變應力行為分析。在不同的溫度( 95－110 °C )與不同的應變速率( 1×10-3 － 5.6×10-2 s-1 )進行塑膠材料拉伸測試變化，研究應變速率與溫度對於ABS塑膠材料之機械性質的影響。同時藉由冪次法則(Power law model)與雙曲線正弦函數(Hyperbolic sine law model)，可以得知應力與應變相關關係式，並探討材料的應變速率(ε ̇)、應力指數(n)、應變速率敏感指數(m)、材料常數(K、A)、熱活化能(Q)與溫度(T)，進而討論其變形條件下的關係式，再由冪次法則與雙曲線正弦函數分別計算出實驗值與計算模擬值，進行組合方程式相關驗證後，比對算出誤差值進而比較。
;This thesis focuses on ABS, which is used in TV set manufacturing with injection molding process, vacuum thermoforming etc. The cost is too high in injection molding process, so we used vacuum thermoforming. The advantage of using a thermoforming process is the cost effective molding in tackling large sized and complex shaped products such as a surfing board, a large size TV set back cover etc.
The combined effects of strain-rate, strain-hardening, and temperature on the elongation deformation behavior of ABS material at a high temperature was proposed. In the vacuum thermoforming process, there will be flow stress at the mold cavity of the ABS plastics, and stress, temperature, strain and strain rate will affect the ABS plastics deformation. The hot deformation behaviors and constitutive analysis of injection molded ABS plastics were systematically investigated by hot tensile tests in the temperature range of 95-110 °C and strain rate range of 1 x 10-3 to 5.6 x 10-2 s-1. Power law and hyperbolic sine constitutive relation was adopted and the constitutive parameters, strain rate ε ̇, stress exponent n, strain rate sensitivity exponent m, material constants (K, A), activation energy Q, and temperature T in the constitutive equations were calculated as a function of strain. By using the two functions, we can compare the calculated flow stresses and experimental ones and get average absolute relative error. |
