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Work Environment and QALT Analysis

The Interface and Work Environment

An intuitive, flexible and integrated work center, ALTA 7's completely updated interface allows you to manage multiple analysis folios and related information all together in a single project file. The new interface provides seamless integration with ReliaSoft's Weibull++ software and includes all the tools you need to extract results and create outstanding plots and reports for your analysis.

Support for a Variety of Data Types

ALTA provides all the tools and options you will need for accelerated life testing data analysis. It is designed for use with complete (non-censored), right censored (suspended), interval or left censored data. Data can be entered individually or in groups. In addition, ALTA makes it easy to alter the data type at any time in the current Data Entry sheet with the Alter Data Type command.

Available Life-Stress Relationships, Distributions and Parameter Estimation

ALTA Standard gives you a choice of the following life-stress models:

• Arrhenius: a single stress model that is typically used for the analysis of data from temperature tests.
• Eyring: a single stress model that is typically used for the analysis of data from temperature or humidity tests.
• Inverse Power Law (IPL): a single stress model that is typically used for the analysis of data from tests with non-thermal stresses, such as vibration, voltage or temperature cycling.
• Temperature-Humidity: a variation of the Eyring relationship that can be used for the analysis of data from temperature and humidity tests.
• Temperature-Nonthermal: a combination of the Arrhenius and IPL relationships that can be used for the analysis of data from tests with two stresses, such as temperature and voltage.

In addition, ALTA PRO offers four additional models for more advanced applications:

New in Version 7!
• Generalized Eyring: used when temperature and a second non-thermal stress (typically voltage) are the acceleration variables.
• Proportional Hazards: analyzes data with up to 8 stress types using the exponential relation. It also allows the use of zero as a stress value, which enables the analysis of data with indicator variables (e.g. on/off or continuous operation).
• General Log-Linear: the most general model, which supports the analysis of data with up to 8 stress types and provides the flexibility of specifying the life-stress relation for each stress (such as Arrhenius and Inverse Power) with the use of transformations.
  Enhanced in Version 7!
• Cumulative Damage: analyzes data with stresses that vary with time. The model now supports multiple time-dependent stresses.

You can select to solve these life-stress relationships combined with an underlying Weibull, exponential or lognormal life distribution. Maximum likelihood estimation (MLE) is used for all parameter calculations.

Need Help Choosing?

You can always rely on ReliaSoft’s Distribution Wizard to determine the best life distribution for your current data. The Distribution Wizard estimates the parameters for each of the selected distributions and compares the log-likelihood values, then recommends the one that best fits your data set.

Theory help is available for each life-stress relationship, underlying life distribution and plot type to help you better understand how ALTA works and how its functions apply to your data. All you have to do is click the Theory help button next to your selection and a window will appear with a brief overview of the principles and theory behind your selection. More in-depth explanations are available in the theoretical textbook and help file that are included with the software.

Managing Stresses

You can use the software to analyze a wide variety of single-stress data, combined stresses or, with ALTA PRO, much more complex stress applications. To help you easily manage the stress types and stress levels in your data sets, the software combines powerful tools with simple interfaces.

• Set use stress levels easily and change them at any time.
• Add or remove stress columns in your data entry sheets quickly and easily. Select which stresses you want to use in your analysis with a single click. ALTA will notify you if there is a mismatch between your selected model and the number of stresses in your data entry sheet or the number of stresses you have selected to use.
  Enhanced in Version 7!
• In ALTA PRO, you can create profiles for stresses that vary over a period of time, such as step-stress, ramp-stress and any other quantifiable stress profile, and use the cumulative damage model to analyze the data. New in Version 7, you can now use the Cumulative Damage model to analyze data with multiple time-varying stresses!
• ALTA PRO's flexible general log-linear and cumulative damage models allow you to analyze data with up to eight simultaneous stress types. You can select a stress transformation (i.e. set the life-stress relationship) for each of the selected stresses in the Stress Relations window.