Extension of durability theory through correlation of wear with acoustic emission to the characteristic values of the ball screw drive

滚珠丝杠传动是目前绝大多数金属切削机床中采用的必不可少的传动元件。因此，准确了解滚珠丝杠传动的使用寿命和保证其可用性具有决定性的经济意义。目前，滚珠丝杠传动的尺寸只考虑疲劳寿命。这是因为滚珠丝杠传动的疲劳寿命、磨损机制和力学行为之间的关系尚不清楚。由于滚珠的复杂运动和返回，滚珠丝杠传动受到复杂和组合磨损机制的影响。这导致了复杂的磨损现象，如磨损、粘连和疲劳。这对滚珠丝杠传动的使用寿命有明显影响。此外，磨损机制影响滚珠丝杠传动的机械特性，例如螺母预紧力或螺母的刚度。目前的磨损诊断方法只关注单个磨损的存在和单个机械特性。因此，对滚珠丝杠传动的磨损机制、磨损存在和机械特性的综合理解目前还不可行。声发射是一种可以观察磨损机制的测量方法。声发射可以更好地提取特征，因为它具有更高的信息密度，从而可以观察到磨损的形成。这是目前用于诊断齿轮箱和轴承。这项研究计划的目的是一个综合的方法，将磨损机制，磨损的存在和滚珠丝杠传动的机械特性随着时间的推移与声发射的使用联系起来。除了用于状态监测的已建立的特征值之外，声发射还构成了一种更精确地识别磨损迹象（例如点蚀）的方法，并将它们在空间上分配到螺母、螺钉或滚珠的轨迹上，从而创建损伤进展的描述。这可以得出有效磨损机制的结论。本研究的目的是将声发射接收的损伤进展描述与机械特性和磨损的存在（结构噪声、温度、摩擦扭矩、螺母预紧力和刚度特征曲线）联系起来。通过对这些观察结果的匹配，可以得出有效磨损机制的时间顺序的结论。此外，通过确定滚珠丝杠传动的静态和动态特性作为磨损发展的函数，对其有效使用寿命和疲劳寿命进行了量化。因此，可以更精确地预测有效使用寿命和疲劳寿命。

Ball screw drives are currently used in the vast majority of all metal cutting machine tools as the essential drive element. Therefore, the precise knowledge of service life and assurance of availability of the ball screw drive is of decisive economic importance. Currently, the dimensioning of ball screw drives only takes into account fatigue life. This is due to the fact that it is unknown how fatigue life, wear mechanisms and the mechanical behavior of the ball screw drive are correlated.Ball screw drives are subjected to complex and combined wear mechanisms due to the complex movement and the return of the ball. This results in complex presences of wear such as abrasion, adhesion and fatigue. This influences distinctively the service life of the ball screw drive. Additionally the wear mechanisms influence the mechanical characteristics of the ball screw drive e.g. the nut preload or stiffness of the nut. Current methods for wear diagnostics only focus on individual presences of wear and on individual mechanical characteristics. Therefore an integrated understanding of wear mechanisms, wear presences and the mechanical characteristics of the ball screw drive is currently not available. Acoustic Emission is a measurement method with which wear mechanisms can be observed. Acoustic Emission allows better feature extraction because of the higher information density, leading to the observation of the formation of wear. This is currently used for diagnostics in gear boxes and bearings.Objective of this research proposal is an integrated approach correlating wear mechanisms, presences of wear and the mechanical characteristics of the ball screw drive over time with the use of Acoustic Emission. In addition to the established characteristic values for condition monitoring, acoustic emission constitutes a method to more precisely identify signs of wear (e.g. pitting) over time and to spatially assign them to the track of nut and screw or ball and therefore create a depiction of damage progression. This allows to draw conclusions on the effective wear mechanisms. This research attains the goal of correlating the depiction of damage progression received with Acoustic Emission with the mechanical characteristics and the presence of wear (structure-borne noise, temperature, frictional torque, nut preload and characteristic curve of stiffness). By matching these observations a conclusion on the chronological sequence of effective wear mechanism can be drawn. Additionally the effective service and fatigue life of the ball screw drive is quantified by identifying static and dynamic properties as a function of wear development. As a result more precise predictions of the effective service and fatigue life can be derived.