新西兰机械工业学论文代写：新型材料
正如已经定义的，这些是可作为结构构件用于建筑目的的创新材料。SMA在结构设计中越来越广泛，并与不同的建筑材料一起使用，如电线（紧固件）或钢筋（如钢筋）。正如在假设中提到的，SMA的类型主要集中在这项研究中，镍和钛合金（NiTi合金），这也是最常见的形状的SMA。
高屈服应力与塑性应变：
形状记忆合金具有随温度变化而改变分子晶体形态的能力，如果附近存在应力区域，形状记忆合金也会发生变化。NiTi形状记忆合金是现代建筑材料中的一种新型材料，其屈服应力高达500兆帕。SMA NiTi的另一个特点是可恢复塑性应变的可观百分比，这种材料能够处理8%的恢复塑性应变，而传统的钢筋仅为0.5%的低数值。
超弹性：
当谈及SMA在易发生变形的情况下所表现出来的特性时，它经历了两个主要的阶段。合金的原始几何图案是立方体形状的，但当合金受到应力状态时，晶体会经历从奥氏体到马氏体的相变，因为这种弯曲会起作用。
结果，当合金回复到奥氏体相时，会发生较大的弹性变形，而保留回到预变形状态。这是一种特殊的性质，NiTi SMA表现在应用应力，晶体结构总是可以恢复，没有退化的晶体。这种行为被称为形状记忆合金的超弹性。
行为改变负载和温度条件下的SMA
此外，理论应力-应变曲线中的材料所显示的路径显示了加载阶段的平坦应力水平，而另一个高原则在卸载阶段处于较低的应力水平。（adedeji，2011）
新西兰机械工业学论文代写：新型材料
As already defined, these are the innovative materials that can be utilized for construction purpose as structural members. SMA is getting widespread as in designing of structures and is used in conjunction with different construction materials in the form of wires (as fasteners) or bars (as reinforcement). As mentioned in the assumptions, the type of SMA focused in this study is alloy of Nickel and Titanium (NiTi) which is also the most common form of SMA.
High yield stress and plastic strain:
The shape memory alloys have the ability to change their molecular crystalline pattern with the change in temperature and it also changes if a stress region is present nearby. The NiTi-based shape memory alloy is referred to as a modern finding in the construction materials and they can be created into any suitable shape and size with the yield stress as high as 500 MPa. Another feature of SMA NiTi is the impressive percentage of recoverable plastic strain that this material is capable of handling 8% of the restoring plastic strain while the traditional steel reinforcement is at a low figure of 0.5% only.
Super-elasticity:
When talking about the property that SMA exhibit under the situations where it is prone to deformations that might occur, it goes through two main types of phases. The original geometry of the alloy is patterned in a cube shape but as the alloy gets subjected to stress condition, the crystals go through phase changes from Austenite to Martensite because of which bending takes effect.
As a result, a large elastic deformation takes place while the retain back to the pre-deformation condition occurs as the alloy gets back into the Austenite phase. This is a special property that NiTi SMA exhibits under applied stress in which crystal structure is always recoverable with no degradation in the crystals. This behaviour is termed as super-elasticity of SMA.
Behaviour of SMA under changing load and temperature condition
In addition, the path followed by the material in the theoretical stress-strain curve shows a flat level of stress in the loading phase, whereas another plateau appears at a lower stress level, during the unloading phase. (Adedeji, 2011)
